The present invention constitutes an improvement in optical devices known in the art as semiconductor ridge waveguide lasers. The basic ridge laser is described in the publication "High yield manufactures of very low threshold, high reliability, 1.3 um varied heterostructure laser diodes grown by metal organic chemical vapor deposition", by "Krakowski M., Blondeau, R., Kazmierski, K., Razeghi, M., Ricciardi, J., Hirtz, P., and DeCremoux, B.,: IEEE J. Lightwave Technol, 1986, LT-4, pp. 1470-1474. and by Jung, H. and Schlosser, E.: "InP/InGaAsP buried mesa ridge laser; A new laser with reduced leakage currents", Appl. Phys. Lett., 1989, 54, pp. 2171-2173.
A typical known ridge waveguide configuration is illustrated in FIG. 1 which is a perspective view wherein only the major elements of the device are shown. The layered structure, grown on a substrate 10, includes at least the active layer 12, sandwiched between cladding layers 14 and 16. The waveguide ridge 18 includes a contact layer 20 and the ridge part 16a of the upper cladding layer 16. Not shown in the drawing are the insulation embedding the sidewalls of the ridge and covering the surface of the upper cladding layer 16, and the metallization layers providing for the electrical contacts to the completed device.
When the device of FIG. 1 is activated by applying proper operating voltages, a light beam 22 is emitted. In the drawing, the light mode region of the laser is shown as a small ellipse centering around the active layer 12 and laterally defined by the stripe ridge 18.
Typical material for the waveguide ridge laser shown in FIG. 1 are N-InP for substrate 10, N-InP for the cladding layer 14, a GaInAsP active layer 12, a P-InP upper cladding layer 16, and a contact layer 20 composed of GaInAs.
The activation of the waveguide ridge laser, whereby electrical current flowing from the ridge part 16a to the substrate 10 through the waveguide layer 12, excites optical radiation 17 which is emitted.